Apparatus for producing seamless tubes



Feb. 2, 1943. A. J. AIKEN 2,309,690

APPARATUS FOR PRODUCING SEAMLESS TUBES INVENTOR. ANDREW (IA/KEN N 06w fm $1.4 190- ATTORNEYS.

a Patented Feb. 2, 1 943 APPARATUS FOR PRODUCING SEAMLESS TUBES Andrew J. Aiken, Cleveland, Ohio Application August 21, 1940, Serial No. 353,487

2 Claims.

This invention relates to an improved apparatus for forming seamless tubes, and more particularly to an improvement directed toward enabling a better control of the size or diameter of the finished tube.

The practice of providing a piercing mill employing a pair of cross rolls and a mandrel for piercing and forming a billetinto a seamless tube is well known, a form of apparatus for this purpose being sh'own in my Patent No. 1,497,467, issued June 10, 1924. In such apparatus, the cross rolls are provided with converging reducing surfaces for reducing or necking down the billet which cooperate with the forward endof the mandrel to pierce the billet. A portion of the mandrel rearwardly of the forward end cooperates with working surfaces on the reducing rolls adjacent the converging surfaces to providea reducing pass in which the wall thickness of the pierced billet is reduced. The cross rolls in effecting a reduction of the wall thickness in the reducing pass impart a lateral flow to the metal causing the sides of the tube between the reducing rolls to bulge away from the sides of the mandrel and take generally an oval shape. In order to control the size or diameter of the tube formed, it is known that this lateral flow or extent of ovality permitted the tube section in the reducing pass must be controlled or limited.

In forming a finished tube, the common practice has been to perform subsequent operations in other mills or roll sets on the tube formed in the piercing mill, and the desirability of eliminating such operations is quite readily apparent.

However, the difficulty of accurately limiting the lateral flow of the metal or ovality of the section in the reducing pass to thereby control the size or diameter of the tube being formed has presented a substantial obstacle toward this end. To control size, it has been proposed to employ various arrangements of guides for limiting the bulge and to cause the tube to elongate. One such expedient has been the provision of rotating guiding rolls for preventing the lateral by reason of the frictional resistance encountered between the moving tube section and the limiting guiding surface. Moreover, the provision of the relatively stationary limiting surface does not enable a uniform and accurate control of the lateral flow of the metal and thereby the ultimate size or diameter of the finished tube.

According to the present invention, there is provided a pair of air hammers for rapid intermittent engagement with the bulged portion of the tube section, and which are adapted to positively deform the bulged section inwardly to limit the extent of lateral flow of metal or ovality permitted the section in the reducing pass, as distinguished from those constructions where a surface is provided for limiting the extent of bulge permitted the section of tube being formed. By deforming the bulged section of the tube inwardly toward the mandrel, the metal ispositively worked and it is thereby possible to accurately control the amount of ovality permitted the tube being formed and the ultimate size of the finished tube, thus readily adapting a piercing mill to the formation of a completely finished tube without the subsequent operations required in the prior art. The intermittent engagement of the'hammers provides less frictional resistance to the rotation of the tube, as compared to stationary limiting surfaces, and thereby reduces the defects resulting from such frictional resistance,

To the accomplishment of the foregoing and related ends, said invention then consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawing and the following description set forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principleof the invention may be used,

In said annexed drawing:

Fig. l is a partial side elevational View of a tube forming mill constructed in accordance with the principles of this invention, parts being broken away centrally thereof and shown in section;

Fig. 2 is a vertical sectional view taken substantially on the line 2-2 of Fig. 1; and

Fig. 3 is a sectional view taken substantially on the line 3-3 of Fig. 1.

Referring'to the drawing, the numeral l indicates a mandrel positioned between a pair of cross rolls 2 and 3 respectively rotatable in opposite directions. Although the cross rolls 2 and 3 illustrated are of the mushroom type, it will be understood that such rolls may be constructed in a barrel or other suitable shape adapted for use in a cross rolling machine.

As best shown in Fig. 2, he cross rolls 2 and 3 are respectively provided with oppositely positioned converging reducing surfaces 4, 4 and diverging surfaces 5, 5 adjoining the converging surfaces. Outwardly of the diverging surfaces 5, 5 the rolls 2 and 3' are provided with parallel reeling surfaces 6, 6 which connect with outwardly curved rounding surfaces I, I.

The mandrel I is positioned in the space between the cross rolls 2 and 3 in such manner that the forward end 8 thereof extends into the space between the converging surfaces 4, 4. The surface 9 of the mandrel rearwardly oi the forward end 8 and lying under the diverging surfaces 5, 5 cooperates with these surfaces to form a reducing pass in which the thickness of the side walls of the pierced billet is reduced in a manner to be described. The mandrel I is formed with a cylindrical portion I positioned between the parallel surfaces 6, 6, and connecting with the surface 9 in the reducing pass.

Stationary guides or steady rests II, I I, adjustably supported on the mill by suitable mechanism, not shown, may be provided for guiding a billet I2 into the mill. Likewise guides I3, mov ably supported on a guideway I4, may be provided for engagement with the end of the formed tube to guide the tube over the support I for the mandrel I.

In forming a seamless tube on a mill of this character, the sides of the tube being formed between the working rolls 2 and 3, will take an oval shape and will bulge away from the sides of the mandrel laterally between the working rolls, as best shown in Fig. 1. This bulging action is due to the fact that the rolls 2 and 3 in reducing the wall thickness of the pierced tube cause the metal to flow laterally outwardly, therebycausing a circumferential growth in the tube section being acted upon. The critical circumferential growth with respect to the ultimate size of. the tube being formed takes place in the reducing pass defined by the diverging surfaces 5, 5 and the tapered surface 9 on the mandrel I, the final reduction in the wall thickness of the tube being formed taking place in this reducing pass.

In order to control the ultimate size or diameter of the tube being formed, it is necessary to accurately control the circumferential growth or extent of ovality permitted the tube section in the reducing pass wherein the last reduction in wall thickness of the tube being formed takes place. For this purpose there is provided a pair of air hammers I6, I6 having hammer heads I1, I! for engagement with the bulging portion of the tube in the reducing pass between the diverging sections 5, 5. Except for the shape of the heads I1, the air hammers I6 may be of any suitable well-known type adapted to impart a rapid reciprocating hammering movement to the heads II, the construction of the operating mechanism for the hammer I 6 forming no particular part of this invention. 7

As best shown in Fig. 1, the longitudinal working surface of the hammer heads II has substantially the contour of the surface 9 of the mandrel I between the diverging sections 5, 5. If desired, the rearward. portion I8 of the hammer heads II may be extended into the space between the converging surfaces 4, 4 for effecting a compacting working action of the metal between these surfaces. The hammers I6 are rearwardly inclined with respect to the direction of forward travel of the tube being formed in order that the hammer heads I I will be able to work the material I over the hump on the mandrel 5 presented by the surface 9 upon a rapid reciprocating movement being imparted thereto.

The preferred construction of the working surface I9 of the hammer heads I! is bestshown in Fig. 3. In this showing. it will be noted that the working surface I9 has a transverse circular contour substantially the same as the mandrel I. The head I! has a surface 20 tangentially connected to the surface I9- and extending in a direction opposed to the direction of rotation of the tube being formed under the influence of the rotation of the cross rolls 2 and 3. In this manner, there is provided a-space underneath the flat surface 20 into which the tube section may flow laterally and expand while the surface I9 is forcing a portion of the bulged section into contact with the mandrel I.

In operation, the billet to be formed into a seamless tube is introduced between the converging sections 4, 4 for a necking down action which cooperates with the end 8 of the mandrel I to pierce the billet. The sections 4, 4 operate to grip the billet and feed-the same forwardly while imparting a rotating movement thereto in the direction of the arrow shown in Fig. 1 in a 0 manner well known in the art. The pierced billet I is thus moved forwardly into the reducing pass, formed between the diverging surfaces 5, 5 and the surface 9 of the mandrel, for a working action adapted, as indicated, to effect a reduction in the wall thickness of the pierced tube. The reciprocating hammers II rapidly and intermittently engage with the bulging sides of the tube section about the forward end of the piercing point to limit the extent or circumferential growth permitted the tube in this reducing pass. The arrangement of the hammers readily adapts itself to variably limiting the extent of bulge or circumferential growth since such hammers ar commonly provided with adjustable mechanism for variably limiting the throw of the hammer head II. By effecting such an adjustment, the bulged section may be deformed inwardly to the desired extent for controlling accurately the ultimate size of the finished tubes.

After being acted on by the diverging surfaces 5, 5 the tube is reeled between the parallel working surfaces 6, 6 and the cylindrical portion ID of the mandrel I. After the reeling operation, the curved flaring surfaces 1, I operate on the tube to remove the ovality in the section thereof and thereby round up the same.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a piercing mill for forming seamless tubes; the combination of a pair of reducing rolls having oppositely disposed converging reducing surfaces and diverging working surfaces and a tapered mandrel disposed between said rolls with its forward end positioned in the space between said converging surfaces and its rearward part between said diverging surfaces and forming a reducing pass with said diverging surfaces; with a pair of rapidly reciprocable hammers respectively 5 positioned between said rolls on opposite sides of 2. Apparatus as claimed in claim 1 wherein said hammers have a flat surface tangentially arranged with respect to the working surfaces thereof and extending in a direction opposed to the direction of rotation of the tube to provide a space permitting a limiting bulging of the side of the tube during a deforming action by said hammer.

' ANDREW J. AIKEN. 

